Aqueous fluoroelastomer curable composition and coated article

ABSTRACT

An aqueous fluoroelastomer curable composition having an aqueous fluoroelastomer dispersion and a basic polyol curing agent, and an article having a coating film formed from this composition. The aqueous fluoroelastomer curable composition has a long pot life although it is a one-fluid type aqueous dispersion, and forms a cured film having sufficient strength and heat resistance at a relatively low temperature in a short time.

FIELD OF THE INVENTION

[0001] The present invention relates to an aqueous fluoroelastomercurable composition and a coated article. In particular, the presentinvention relates to an aqueous fluoroelastomer curable compositioncomprising a fluorine-containing copolymer and a specific polyol curingagent, and an article having a coating film formed from such acomposition.

BACKGROUND ART

[0002] A method for curing an aqueous fluoroelastomer coatingcomposition with a polyamine curing agent is known (see JP-B-58-53671corresponding to U.S. Pat. No. 4,339,553). In general, the coating filmformed by this method has good mechanical properties, but low sealingproperties. In addition, when such a coating film is used to coat thesurface of a roll used in office automation (OA) equipment (e.g. copyingmachines, printers, etc.), it has drawbacks such as insufficientelasticity, heat resistance, and so on. When the polyamine curing agentis added to a fluoroelastomer curable composition, for example, acoating composition, its pot life is shortened because of gelling, etc.Accordingly, two or more fluid type compositions are practicallysupplied, but no practically usable one-fluid type composition isavailable.

[0003] When a fluoroelastomer is cured with a polyol curing agent, it ispossible to prepare one-fluid type fluoroelastomer coating compositionscontaining organic solvents (see PCT/JP97/02853). However, in theseyears, the VOC regulation and the like become severer and severer, andthus environment friendly aqueous coating compositions are desired.However, one-fluid type aqueous fluoroelastomer coating compositions inthe form of an aqueous dispersion containing no organic solvent are notknown.

DISCLOSURE OF THE INVENTION

[0004] One object of the present invention is to provide a one-fluidtype aqueous fluoroelastomer curable composition, which can beformulated as an aqueous dispersion, form a cured film having highstrength at a relatively low temperature in a short time, and has a longpot life.

[0005] Another object of the present invention is to provide a coatedarticle, which does not suffer from the drawbacks of coated articleshaving a coating film formed from a conventional aqueous fluoroelastomercoating composition, in particular, rolls for OA equipment.

[0006] To achieve these and other objects, the present inventionprovides an aqueous fluoroelastomer curable composition comprising anaqueous fluoroelastomer dispersion and a basic polyol curing agent, anda coated article at least a part of the surface of which is coated witha coating layer formed from such a composition.

EMBODIMENTS TO CARRY OUT THE INVENTION

[0007] Now, the components contained in the composition of the presentinvention will be explained.

[0008] (A) Aqueous Dispersion of Fluoroelastomer

[0009] The aqueous dispersion of a fluoroelastomer is prepared bydispersing a fluorine-containing elastic copolymer in water in aconcentration of 10 to 75 wt. % in the presence of a surfactant such aspolyoxyethylene, an alkyl phenyl ether, an alkylsulfonate salt, etc.

[0010] The fluorine-containing elastic copolymer is afluorine-containing copolymer comprising repeating units represented bythe formula: —CH₂— in the backbone. Typical examples of such a copolymerinclude fluorine-containing elastic copolymers comprising vinylidenefluoride, and specific examples of such copolymers are those comprisingthe following repeating units in the backbone:

[0011] at least one repeating unit selected from the group consisting of—CF₂—CH₂—, —CH₂—CH₂— and —CH₂—CH(CH₃)— and

[0012] at least one repeating unit selected from the group consisting of—CF₂—CF(CF₃)—, —CF₂—CF₂— and —CF₂—(ORf)CF— in which Rf is a fluoroalkylgroup having 1 to 6 carbon atoms.

[0013] Specific examples of such copolymers include vinylidenefluoride-hexafluoropropylene copolymers, vinylidenefluoride-tetrafluoroethylene-hexafluoropropylene copolymers,ethylene-hexafluoropropylene copolymers, tetrafluoroethylene-propylenecopolymers, etc. Such fluorine-containing elastic copolyers arecommercially sold under the trade names of “DAIEL®” (by DaikinIndustries Ltd.), “BAITON FLOAM®” (by E.I DuPont), “AFLAS®” (by ASAHIGLASS Co., Ltd.), and so on. Among them, the vinylidene fluoride basecopolymers are preferable in view of the crosslinkability.

[0014] (B) Basic Polyol Curing Agent

[0015] Herein, the basic polyol curing agent means a compound or apolymeric compound having at least two hydroxyl groups, in particular,phenolic hydroxyl groups in the molecule, and the curing ability.

[0016] Examples of the polyol curing agent includes salts of a basiccompound with a phenol compound of the formula:

[0017] or a phenolic resin of the formula:

[0018] wherein Z is —CH₂— or —CH₂OCH₂—, Y is a hydrogen atom, a halogenatom, or a group of the formula: —R, —CH₂OR or —OR in which R is analkyl group having 1 to 4 carbon atoms, and n is an integer of 0 to 100.

[0019] Examples of the basic compound include ammonium, phosphonium,alkali metals (e.g. lithium, sodium, potassium, etc.), alkaline earthmetals (e.g. beryllium, magnesium, calcium, barium, etc.), and so on.

[0020] Among them, the salts of hydroquinone, bisphenol A, bisphenol AF,resol type phenolic resins, etc. are preferable in view of theproperties of the coating films.

[0021] As a curing agent, a combination of the above basic polyol andother polyol may be used.

[0022] (C) Curing Accelerator

[0023] The composition of the present invention may contain thefollowing compound as an optional curing accelerator:

[0024] Quaternary Ammonium Salt

[0025] A quaternary ammonium salt of the formula:

NR₄X or R₃N—R′—NR_(3.)2X

[0026] wherein X is an acid residue or a hydroxyl group, R groups arethe same or different and each an alkyl group having 1 to 20 carbonatoms, an halogenated alkyl group having 1 to 20 carbon atoms or an arylgroup having 6 to 20 carbon atoms, or two or more R groups together forma carbon ring or a heterocyclic group, and R′ is an alkylene grouphaving 2 to 21 carbon atoms or a phenylenedialkylene group having 8 to12 carbon atoms.

[0027] Examples of the acid residue include halide, sulfate, sulfite,bisulfite, thiosulfate, sulfide, polysulfide, hydrogen sulfide,thiocyanate, carbonate, bicarbonate, nitrate, carboxylate, borate,phosphate, biphosphate, phosphite, perchlorate, bifluoride, arsenate,ferricyanide, ferrocyanide, molybdate, selenate, selenite, uranate,tungstate, etc.

[0028] Specific examples of the quaternary ammonium salt includequaternary alkyl- and aralkyl-ammonium salts (e.g.trimethylbenzylammonium chloride, triethylbenzylammonium chloride,dimethyldecylbenzylammonium chloride, triethylbenzylammonium chloride,myristylbenzyldimethylammonium chloride, dodecyltrimethylammoniumchloride, dimethyltetradecylbenzylammonium chlroride,trimethyltetradecylammonium chloride, coconuttrimethylammonium chloride,stearyltrimethylammonium chloride, distearyldimethylammonium chloride,tetrabutylammonium hydroxide,1,4-phenylenedimethylenebistrimethylammonium dichloride,1,4-phenylenedimethylenebistriethylammonium dichloride,ethylenebistriethylammonium dibromide, etc.), quaternary1,8-diaza-bicyclo[5.4.0]-7-undecenium salts (e.g.8-methyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium chloride,8-methyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium iodide,8-methyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium hydroxide,8-methyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium methylsulfate,8-methyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium bromide,8-propyl-8-diaza-bicyclo[5.4.0]-7-undecenium bromide,8-dodecyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium chloride,8-dodecyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium hydroxide,8-eicosyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium chloride,8-tetracosyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium chloride,8-benzyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium chloride,8-benzyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium hydroxide,8-phenetyl-1,8-diaza-bicyclo[5.4.0]-7-undecenium chloride,8-(3-phenylpropyl)-1,8-diaza-bicyclo[5.4.0]-7-undecenium chloride,etc.), and the like.

[0029] Furthermore, as curing accelerators, quaternary salts of thefollowing tertiary amines with inorganic or organic acids can be used:

[0030] Tertiary Amine

[0031] A tertiary amine of the formula:

NR₃ or R₂N—R′—NR₂

[0032] wherein R groups are the same or different and each an alkyl oralkenyl group having 1 to 20 carbon atoms, or an aryl group having 6 to20 carbon atoms, or two or more R groups together form a carbon ring ora heterocyclic group, and R′ is an alkylene group having 2 to 21 carbonatoms or a phenylenedialkylene group having 8 to 12 carbon atoms.

[0033] Specific examples of the tertiary amines include trimethylamine,triethylamine, tri-n-propylamine, tri-n-butylamine, triisobutylamine,methyldiethylamine, dimethylethylamine, dimethyl-n-propylamine,dimethyl-n-butylamine, dimethylisobutylamine, dimethylisopropylamine,dimethyl-sec.-butylamine, dimethyl-tert.-butylamine, triallylamine,diallylmethylamine, allyldimethylamine, bensyldimethylamine,benzyldiethylamine, N-allylpiperidine, N-ethylpiperidine,N-butylpiperizine, N-methylpyrrolidine, N-cyclohexylpyrrolidine,N-n-butylpyrrolidine, N-ethylpyrrolidine, N-benzylpyrrolidine,2,4,6-trimethylpyridine, etc.

[0034] Examples of the inorganic or organic acids which form thequaternary salts include HCl, HBr, HF, (C₂H₅)₃NH⁺Cl⁻, (C₂H₅)₃NH⁺NO³⁻,2(C₂H₅)₃NH⁺SO₄ ²⁻, 2(C₂H₅)₃NH⁺CO₃ ²⁻, (C₂H₅)₃NH⁺RO⁻, (C₂H₅)₃NH⁺RCOO⁻,(C₄H₉)₃NH⁺Cl⁻, (C₄H₉)₃NH⁺NO₃ ⁻, 2(C₄H₉)₃NH⁺SO₄ ²⁻, 2(C₄H₉)₃NH⁺CO₃ ²⁻,(C₄H₉)₃NH⁺RO⁻, (C₄H₉)₃NH⁺RCOO⁻ wherein R is an alkyl or alkenyl grouphaving 1 to 20 carbon atoms or an aryl group having 6 to 20 carbonatoms.

[0035] Primary or secondary amines are not preferable since they inducereactions other than the polyol curing. Amines having pKa of less than 8are not preferable, since they achieve the low curing rate and thus thecoating film has low strength.

[0036] In the present invention, an organic acid may be added to thecomposition to improve the shelf stability of the composition. As theorganic acid, one having 1 to 12 carbon atoms, preferably 1 to 4 carbonatoms is used. Among them, those having 9 or more carbon atoms are lesspreferable since they remain in the coating film formed from thecomposition. Preferred organic acids are monocarboxylic acids such asformic acid, acetic acid, propionic acid, etc. and dicarboxylic acidssuch as oxalic acid, malonic acid, succinic acid, etc.

[0037] The organic acids suppress the polyol curing of thefluorine-containing copolymer contained in the composition during thestorage. When the composition is coated, dried and baked, the organicacid is evaporated or thermally decomposed, the basic compoundaccelerates the curing reaction. Thus, the organic acid is categorizedinto “curing accelerators” in the present invention.

[0038] The compounded amounts of the components in the compositionaccording to the present invention are as follows:

[0039] The basic polyol curing agent is used in an amount of 0.1 to 10wt. parts, preferably 0.5 to 5 wt. parts, and the curing accelerator isused in an amount of 0 to 10 wt. parts, preferably 0.01 to 5 wt. parts,all based on 100 wt. parts of the fluorine-containing copolymer.

[0040] When the amount of the curing accelerator is less than the abovelower limit, it may be difficult to cure the copolymer. When the amountof the curing accelerator exceeds the above upper limit, it may bedifficult to control the curing.

[0041] In addition to the polyol curing agent and the curingaccelerator, the composition of the present invention may containvarious additives which are usually added to the fluoroelastomercompositions, for example, fillers, colorants, acid-acceptors, etc.

[0042] Examples of the filler include carbon black, white carbon,calcium carbonate, barium sulfate, etc., and examples of the colorantinclude inorganic pigments, mixed oxide pigments, etc.

[0043] Examples of the acid-acceptor include magnesium oxide, leadoxide, zinc oxide, lead carbonate, zinc carbonate, and complex saltssuch as hydrotalcite. Acid-acceptors having a high activity such ascalcium hydroxide are less preferable since the composition tends togel. Acid-acceptors having lower pKa than that of the above basiccompounds are preferable. When the acid-acceptors have high pKa, thecomposition tends to gel. In general, the acid-acceptor is used in anamount of 1 to 40 wt. parts per 100 wt. parts of the fluorine-containingcopolymer in accordance with the activity of the acid-acceptor.

[0044] Furthermore, the composition of the present invention may contain5 to 900 wt. parts of a fluororesin or a terminal-modifiedperfluoropolyether (a perfluoropolyether compound having a terminalfunctional group reactive with the fluorine-containing copolymer such as—NH₂, —CH₂OH, etc.) per 100 wt. parts of the fluorine-containingcopolymer. Thereby, the non-stick property can be imparted to thecoating film formed from the composition.

[0045] Examples of the fluororesin include polyvinylidene fluoride(PVdF), ethylene-tetrafluoroethylene copolymers (ETFE),polychlorotrifluoroethylene (CTFE),tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ethercopolymer (EPA), tetrafluoroethylene-hexafluoropropylene copolymers(FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA),polytetrafluoroethylene (PTFE), etc. Among them, tetrafluoroethylenebase copolymers are preferable in view of the non-stick property. Thefluororesins are preferably used in the form of an aqueous dispersion inview of the dispersibility.

[0046] The composition of the present invention can be applied and curedin the same manners as those used to apply and cure the conventionalcurable compositions of the fluorine-containing copolymers. That is,according to the properties of the compositions, they are applied to anarticle to be coated by brush coating, spray coating, dip coating, flowcoating, dispenser coating, screen coating, etc., and sufficientlydried, followed by baking at a temperature of 150 to 300° C. for 10 to120 minutes.

[0047] The surface of the article to be coated is preferably defatted orwashed. It is also preferable to form a primer layer on the surface ofthe article to be coated to improve the adhesion of the composition tothe article. Examples of the primer include silane primers, siliconeprimers, etc.

[0048] A surface layer may be formed on the coating film formed from thecomposition of the present invention. The surface layer can be formedfrom the above fluororesins and/or the terminal-modifiedperfluoropolyethers by conventional methods.

[0049] The curable composition of the fluorine-containing elasticcopolymer according to the present invention is characterized in that ithas better shelf stability than an aqueous composition curable with apolyamine curing agent, although the composition of the presentinvention is a one-fluid type aqueous dispersion. Furthermore, thecomposition of the present invention can contain the solid of thefluorine-containing copolymer at a higher concentration than thesolvent-based polyol-curing composition.

[0050] Examples of articles or substrates to be coated with thecomposition of the present invention are as follows:

[0051] metals (e.g. iron, stainless steel, copper, aluminum, brass,etc.), glass products (e.g. glass plates, woven and non-woven fabric ofglass fiber, etc.), molded articles or coated articles of general resinsor heat-resistant resins (e.g. polypropylene, polyoxymethylene,polyimide, polyamideimide, polysulfone, polyethersulfone, polyetherether ketone, etc.), molded articles or coated articles of generalrubbers (e.g. styrene-butadiene rubber (SBR), isobutylene-isoprenerubber, nitrile-butadiene rubber (NBR), etyrene-propylene rubber (EPDM),etc.) and heat-resistant rubbers (e.g. silicone rubber, fluoroelastomer,etc.), woven and non-woven fabric of natural and synthetic fibers, andthe like.

[0052] The coating layers formed from the composition of the presentinvention can be used in various fields which require heat resistance,solvent resistance, lubrication and/or non-stick properties. Specificexamples of the applications include rolls (e.g. fixing rolls, pressrolls, etc.) and conveying belts for OA equipment such as copyingmachines, printers, facsimiles, etc.; sheets and belts; O-rings,diaphragms, chemical-resistant tubes, fuel hoses, valve seals, gasketsfor chemical plants, engine gaskets, and the like.

EXAMPLES

[0053] The present invention will be illustrated by the followingexamples.

Example 1

[0054] Preparation of Pigment Paste A

[0055] A filler (MT carbon black) (20 wt. parts) and an acid-acceptor(MA-150 manufactured by KYOWA CHEMICAL INDUSTRIES, Ltd.; main component:MgO) (3 wt. parts) were dispersed in pure water (48 wt. parts) togetherwith a surfactant (HS-208 manufactured by NFO Corporation; 20% aqueoussolution; main component: C₈H₁₇-p-Ph—O—(CH₂CH₂O)_(n)—OH (n=8)) (2 wt.parts) to obtain a paste, which is referred to as “Pigment Paste A”.

[0056] Preparation of Coating Composition

[0057] Pigment Paste A (73 wt. parts) and a surfactant (ADEKANOL UH-14osmanufactured by ASAHI DENKA KOGYO Co., Ltd.; main component: polymericnonionic surfactant) (1.5 wt. parts) were added to the dispersion of afluoroelastomer (DAIEL G-501 AN manufactured by Daikin Industries Ltd.;vinylidene fluoride-tetrafluoroetylene-hexafluoropropylene copolymer)(100 wt. parts of the solid component), and well dispersed. Then, tothis aqueous dispersion, the sodium salt of bisphenol AF (2.2 wt. parts)as a basic polyol curing agent and the octylate salt of DBU(1,8-diaza-bicyclo[5.4.0]-7-undecene) (U-CAT SA102 manufactured bySAN-APRO Co., Ltd.) (0.5 wt. part) as a curing accelerator were added toobtain a coating composition.

[0058] With the obtained coating composition, the stability of thecomposition and the mechanical property of the coating film weremeasured by the following methods:

[0059] Stability

[0060] The coating composition was poured in a polyethylene bottle andkept standing at 25° C. After 2 days, 7 days, 2 weeks, 1 month and 2months, the state of the coating composition was observed.

[0061] Mechanical Properties

[0062] The coating composition was poured in a metal vat and dried atroom temperature for 5 days and then at a temperature of 80 to 100° C.for 2 days, followed by baking at 200° C. for 60 minutes. The formedfilm was peeled off from the vat. Then, a JIS No. 5 dumbbell-shapedsample was punched out from the film and subjected to the tensile testat a pulling rate of 500 mm/min.

Example 2

[0063] A coating composition was prepared in the same manner as inExample 1 except that sodium salt of hydroquinone was used in place ofthe sodium salt of bisphenol AF.

Example 3

[0064] A coating composition was prepared in the same manner as inExample 1 except that a phenolic resin soluble in an alkaline water(DKK-1 manufactured by ASAHI ORGANIC MATERIAL INDUSTRIES, Ltd.) was usedin place of the sodium salt of bisphenol AF.

Example 4

[0065] A coating composition was prepared in the same manner as inExample 1 except that DAIEL G-701 BP dispersion (manufactured by DaikinIndustries Ltd.; vinylidene fluoride-hexafluoropropylene copolymerdispersion) was used in place of the DAIEL G-501 AN dispersion.

Example 5

[0066] A coating composition was prepared in the same manner as inExample 1 except that DAIEL G-701 BP dispersion (manufactured by DaikinIndustries Ltd.; vinylidene fluoride-hexafluoropropylene copolymerdispersion) was used in place of the DAIEL G-501 AN dispersion, andsodium salt of hydroquinone was used in place of the sodium salt ofbisphenol AF.

Example 6

[0067] A coating composition was prepared in the same manner as inExample 1 except that DAIEL G-701 BP dispersion (manufactured by DaikinIndustries Ltd.; the dispersion of vinylidenefluoride-hexafluoropropylene copolymer) was used in place of the DAIELG-501 AN dispersion, and a phenolic resin soluble in an alkaline water(DKK-1 manufactured by ASAHI ORGANIC MATERIAL INDUSTRIES, Ltd.) was usedin place of the sodium salt of bisphenol AF.

Comparative Example 1

[0068] A coating composition was prepared in the same manner as inExample 1 except that bisphenol A was used in place of the sodium saltof bisphenol AF.

Comparative Example 2

[0069] A coating composition was prepared in the same manner as inExample 1 except that a polyamine curing agent (EPOMATE F-100manufactured by YUKA SHELL Co., Ltd.) (2 wt. parts) and a silanecoupling agent (A-1100 manufactured by Nippon Unicar Co., Ltd.) (9 wt.parts) were used in place of the polyol curing agent and the curingaccelerator, respectively, and pure water (7.5 wt. parts) was used.

[0070] The compositions and the results of the experiments in Examples1-6 and Comparative Examples 1-2 are summarized in Table 1. TABLE 1Component (wt. %) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 C. Ex. 1 C. Ex. 2Fluoroelastomer dispersion: DAIEL G501AN 100 100 100 100 100 DAIELG701BP 100 100 100 Filler: MT-carbon black 20 20 20 20 20 20 20 20Acid-acceptor: MA-150 3 3 3 3 3 3 3 3 Surfactant ADEKANOL UH-140S 1.51.5 1.5 1.5 1.5 1.5 1.5 1.5 Polyol curing agent: Na salt of bisphenol AF2.2 2.2 — Na salt of hydroquinone 2.2 2.2 — DKK-1* 2.2 2.2 — Bisphenol A2.2 — Curing accelerator: SA-102 0.5 0.5 0.5 0.5 0.5 0.5 0.5 — Polyaminecuring agent: Epomate E-100 — — — — — — — 2 Silane coupling agent:A-1100 — — — — — — — 9 Stability Gelled No Gelled Gelled No No Immedi-Gelled after 7 change after 2 after 7 change change ately in 2 days daysafter 3 weeks days after 3 after 3 gelled months months months 100%Modulus 13 14 20 15 12 23 — 69 (kgf/cm²) Tensile strength 67 57 68 43 4069 — 110 (kgf/cm²) Elongation 590 820 780 570 1000 740 — 240 (%)

Example 7

[0071] With the coating film formed from a coating composition, whichwas prepared in the same manner as in Example 3, the adhesion property,non-stick property and tensile property was measured as follows:

[0072] Adhesion Properties

[0073] The coating composition was spray coated on a substrate, welldried at 80 to 100° C. and baked at 200° C. for 60 minutes.

[0074] On the surface of the coating film, crosshatches (100 squares)were formed according to JIS K 5400-1990, 8.5.2, and an adhesive tape(manufactured by NICHIBAN) was closely adhered to the cross-hatchedsurface, and immediately peeled off. Using fresh adhesive tapes, thepeeling was repeated 10 times, and the number of the remaining squareswas counted.

[0075] As the substrates, an aluminum plate (A-1050), a polyimide film,a silicone rubber sheet and a fluoroelastomer sheet were used.

[0076] The aluminum plate was beforehand sand blasted, and coated with asilane compound (LORD Chemlok Y-4310; 10 wt. % aqueous solution) as aprimer. The silicone rubber sheet was also coated with GLP-103SR(manufactured by Daikin Industries Ltd.; main component: silicone resin)as a primer.

[0077] Non-Stick Property

[0078] On the surface of the coating film, which was prepared in thesame manner as in the test of the adhesion properties, one drop of purewater or n-cetane was dropped, and a contact angle was measured with agoniometer (manufactured by KYOWA KAIMEN KAGAKU KABUSHIKIKAISHA).

[0079] Mechanical Property

[0080] The mechanical property was measured in the same manner as inExample 1.

Example 8

[0081] The adhesion properties, non-stick property and mechanicalproperty was measured in the same manner as in Example 7 except that acoating composition, which was prepared in the same manner as in Example6, was used.

Comparative Example 3

[0082] The adhesion properties, non-stick property and mechanicalproperty was measured in the same manner as in Example 7 except that acoating composition, which was prepared in the same manner as inComparative Example 1, was used.

Comparative Example 4

[0083] The adhesion properties, non-stick property and mechanicalproperty was measured in the same manner as in Example 7 except that asolvent-based polyol curable fluoroelastomer coating composition (avinylidene fluoride-hexafluoropropylene copolymer base coatingcomposition manufactured by Daikin Industries Ltd.) was used as acoating composition, and the coating composition was coated on thesubstrate with a bar coater to form the coating film for the measurementof the adhesion properties and non-stick property.

Example 9

[0084] Preparation of Pigment Paste B

[0085] A filler (TALOX R-516L manufactured by TITANIUM INDUSTRIES, Ltd.;main component: Fe₂O₃) (3 wt. parts) and an acid-acceptor (MA-150manufactured by KYOWA CHEMICAL INDUSTRIES, Ltd.) (3 wt. parts) weredispersed in pure water (43 wt. parts) together with a surfactant(HS-208 manufactured by NFO Corporation; 20% aqueous solution) (2 wt.parts) to obtain a paste, which is referred to as “Pigment Paste B”.

[0086] Preparation of Coating Composition

[0087] Pigment Paste B (51 wt. parts) and a surfactant (ADEKANOL UH-140Smanufactured by ASAHI DENKA KOGYO Co., Ltd.) (3.5 wt. parts) were addedto the dispersion of a fluoroelastomer (DAIEL G-501 AN manufactured byDaikin Industries Ltd.; vinylidenefluoride-tetrafluoroetylene-hexafluoropropylene copolymer) (100 wt.parts of the solid component), and a FEP dispersion (manufactured byDaikin Industries Ltd.; solid content: 52 wt. %) (192 wt. parts) and asurfactant (NONION DS-60HN manufactured by NFO Corporation) were added,and the mixture was well dispersed. Then, to this aqueous dispersion, analkaline water-soluble phenolic resin (DKK-1) (2.2 wt. parts) as a basicpolyol curing agent and the octylate salt of DBU(1,8-diaza-bicyclo-[5.4.0]-7-undecene) (U-CAT SA102 manufactured bySAN-APRO Co., Ltd.) (0.5 wt. part) as a curing accelerator were added toobtain a coating composition.

[0088] With a coating film formed from the obtained coating composition,the adhesion properties, non-stick property and mechanical property wasmeasured as follows:

[0089] Adhesion Properties and Non-Stick Property

[0090] The coating composition was spray coated on a substrate, welldried at 80 to 100° C. and baked at 300° C. for 15 minutes. Then, theadhesion properties and non-stick property was measured in the samemanners as those described in Example 7.

[0091] Mechanical Property

[0092] The coating composition was spray coated on an aluminum foil,well dried at 80 to 100° C. and baked at 300° C. for 15 minutes. Thealuminum foil was dissolved with hydrochloric acid. Then, a JIS No. 4dumbbell-shaped sample was punched out from the film and subjected tothe tensile test at a pulling rate of 500 mm/min.

Example 10

[0093] A coating composition was prepared in the same manner as inExample 9 except that DAIEL G-701 BP dispersion was used in place ofDAIEL G-501 AN dispersion, and the adhesion properties, non-stickproperty and mechanical property of the coating film were measured.

Comparative Example 5

[0094] The procedures of Example 9 were repeated except that a FEP-addedaqeueous polyamine curable fluoroelastomer coating (a vinylidenefluoride-tetrafluoroethylene-hexafluoropropylene copolymer base coatingcomposition; ratio of fluoroelastomer to fluororesin (solidcontent)=1:1) cured with the diamine agent to obtain a coatingcomposition, and the adhesion properties, non-stick property andmechanical property of the coating film were measured.

Example 11

[0095] The coating composition prepared in Example 9 was spray coated onthe substrate and well dried at 80 to 100° C. Then, a FEP powder coating(manufactured by Daikin Industries Ltd.) was coated on the dried filmand then baked at 300° C. for 15 hours. The adhesion properties andnon-stick property of the coating film were measured in the same mannersas in Example 9.

[0096] The results of the measurements in Examples 9-11 and ComparativeExamples 3-5 are summarized in Table 2. TABLE 2 Properties Ex. 7 Ex. 8C. E. 3 C. Ex. 4 Ex. 9 Ex. 10 C. Ex. 5 Ex. 11 Adhesion properties(crosshatch test) Substrate: Aluminum 100/100 100/100 100/100 100/100100/100 100/100 100/100 100/100 Polyimide 100/100 100/100 100/100100/100 100/100 100/100 100/100 100/100 Silicone rubber 100/100 100/100100/100 100/100 100/100 100/100 100/100 100/100 Fluororubber 100/100100/100 100/100 100/100 100/100 100/100 100/100 100/100 Non-stickproperty (contact angle) Pure water 95 97 93 96 105 106 104 106 n-Cetane40 44 39 41 55 55 51 55 Mechanical properties 100% Modulus 20 23 69 4055 60 120 — (kgf/cm²) Tensile strength 68 69 110 90 85 85 140 —(kgf/cm²) Elongation 780 740 240 290 320 290 210 — (%)

1. An aqueous fluoroelastomer curable coating composition comprising: anaqueous fluoroelastomer dispersion; a basic polyol curing agent; acuring accelerator selected from the group consisting of salts oftertiary amines of the formula NR₃ with inorganic or organic acids andsalts of tertiary amines of the formula R₂N—R′— NR₂ with inorganic ororganic acids; and optionally at least one fluoropolymer selected fromthe group consisting of a fluororesin and a terminal-modifiedperfluoropolyester; wherein each of the R groups in either formula forthe curing accelerator is the same or different from each other and eachis an alkyl or alkenyl group having 1 to 20 carbon atoms, or an arylgroup having 6 to 20 carbon atoms, or two or more R groups together forma carbon ring or a heterocyclic group, and R′ is an alkylene grouphaving 2 to 21 carbon atoms or a phenylenedialkylene group having 8 to12 carbon atoms.
 2. The aqueous fluoroelastomer curable compositionaccording to claim 1, wherein said basic polyol curing agent is a saltof a polyol having a phenyl group and at least two hydroxyl groups witha basic compound.
 3. The aqueous fluoroelastomer curable compositionaccording to claim 1, wherein said basic polyol curing agent is a saltof a polyol having a phenyl group and at least two hydroxyl groups withat least one basic compound selected from the group consisting ofammonium, phosphonium, alkali metals and alkaline earth metals.
 4. Theaqueous fluoroelastomer curable composition according to claim 1,wherein said basic polyol curing agent is a salt of at least one polyolselected from the group consisting of hydroquinone, bisphenol A,bisphenol AF and resol type phenolic resins and at least one basiccompound selected from the group consisting of ammonium, phosphonium,alkali metals and alkaline earth metal.
 5. The aqueous fluoroelastomercurable composition according to claim 1, wherein said fluoroelastomeris an elastic copolymer of vinylidene fluoride and at least one otherethylenically unsaturated fluorine-containing monomer copolymerizabletherewith.
 6. The aqueous fluoroelastomer curable composition accordingto claim 1, wherein said aqueous fluoroelastomer dispersion in saidcoating composition comprises a fluorine-containing elastic copolymerhaving repeating units represented by the formula: —CH₂— in thebackbone.
 7. The aqueous fluoroelastomer curable composition accordingto claim 1, said aqueous fluoroelastomer curable composition comprisessaid fluororesin.
 8. The aqueous fluoroelastomer curable compositionaccording to claim 7, wherein said fluororesin is a tetrafluoroethylenebase polymer.
 9. The aqueous fluoroelastomer curable compositionaccording to claim 7, wherein said fluororesin is a copolymer oftetrafluoroethylene with at least one monomer selected from the groupconsisting of hexafluoropropylene and a perfluoroalkyl vinyl ether. 10.The aqueous fluoroelastomer curable composition according to claim 1,said aqueous fluoroelastomer curable composition comprises saidterminal-modified perfluoropolyether.
 11. The aqueous fluoroelastomercurable composition according to claim 7, said aqueous fluoroelastomercurable composition comprises the terminal-modified perfluoropolyether.12. An article wherein at least a part of the surface of said article iscoated with a coating layer formed from the aqueous fluoroelastomercurable coating composition according to claim 1, wherein said coatinglayer is further coated with a non-tacky layer of fluororesin.
 13. Anarticle wherein at least a part of the surface of said article is coatedwith a coating layer formed from the aqueous fluoroelastomer curablecoating composition according to claim 7, wherein said coating layer isfurther coated with a non-tacky layer of fluororesin.
 14. An articlewherein at least a part of the surface of said article is coated with acoating layer formed from the aqueous fluoroelastomer curable coatingcomposition according to claim 10, wherein said coating layer is furthercoated with a non-tacky layer of fluororesin.